^{Picture credit: Civil Aviation Tabloid}

The images were uploaded on the popular chat app WeChat, and were later labelled as bullying by online users.

The post said the cabin crew, who worked for Kunming Airlines, were "forced into lockers by security staff upon completing 30 to 50 hours of service" as part of an "industry ritual".

Kunming Airlines has issued a statement saying it was investigating the matter.

The company has insisted that the incident occurred after the crew had completed their duties and that the safety of the flight was not affected, the BBC said.

The airline also added that it had never received complaints from its cabin crew.

"The company attaches high importance to this incident and will prevent such things from happening again," the statement said.

According to the official Facebook page of Chinese state broadcaster CCTV News, although many of the female cabin crew members were "annoyed" by the ritual, they still went through it in fear of not being accepted by their senior colleagues.

"Multiple stewardesses have also consistently filed complaints to the company but their requests were ignored and the ritual continued," it said in the Facebook post.